The invention relates generally to rotary cutters for cutting web or sheet material, and more particularly to a knife holder apparatus which may be attached to a knife cylinder and employed with an associated anvil cylinder to transversely cut or score a moving web or sheet.
It is conventional practice to use a rotary cutter to transversely cut web material received from a printing press. In general, rotary cutters have an anvil cylinder and a knife cylinder which are rotatable in timed relation. One or more knife holders, which hold the cutting knives, are attached to the knife cylinder. The knife and anvil cylinders normally rotate at the same speed and the moving paper or web material is transversely cut or scored as the cutting knife moves into and out of engagement with the anvil surface. The cutting knives may be spaced apart to create the desired cut.
In the conventional rotary cutter, knife replacement is a time-consuming operation. Moreover, because of the increased use of recycled paper and its negative effect on the life of the cutting knife, reducing the time required for the knife replacement operation has become even more important.
To reduce down time due to blade replacement, unitary epoxy knife holder and blade assemblies have been employed. An example of a unitary epoxy knife holder and blade assembly 112 is shown in FIG. 10. Replacement of a worn cutting knife of this type, however, requires that the entire assembly be removed from the knife cylinder, which requires stripping away the cushioning and rubber material which is placed over the knife cylinder and portions of the holder. The installer must then realign and remount the replacement holder on the knife cylinder.
To avoid the above-mentioned problems associated with unitary knife holder and blade assemblies, the knife holder assembly as shown in FIG. 11 has been developed. This knife holder assembly includes a metal holder 116 and a backing member 110, which locks a cutting rule 114 to the holder 116 with holding screws 118. Although this knife holder assembly does not require the complete removal of the holder 116 from the knife cylinder, it does require some of the cushioning material to be stripped back because the release screws 118 are located on the side of the holder. This requires the person changing the cutting rule 114 to loosen the holding screws 118 from the side of the holder, which is both awkward and time consuming.
U.S. Pat. No. 5,893,314 discloses an improved knife holder assembly that overcomes some of the problems associated with the knife holder assembly shown in FIG. 11. An example of this type of improved knife holder assembly is shown in FIG. 12. This knife holder assembly 200 includes a holder 202, and an adjusting member 204 that allows the operator to replace the knife 206 by loosening the fasteners 208 from the top portion of the holder. This eliminates the need to pull back or remove the cushioning material to get at side mounted fasteners 212. However, this apparatus requires a significant number of screws to adequately secure the multiple adjusting members. This apparatus is also expensive to manufacture.
It would be desirable to have an uncomplicated and inexpensive knife holder assembly that would allow the user to quickly and efficiently remove the worn cutting knife and replace it without removing the holder from the knife cylinder.